[css-typed-om] Consider using properties in addition to .get/.set

[esprehn]

Real properties are faster since we can cache the property lookup, ex.

element.styleMap.color // => JS VM can cache the lookup for color

It also lets the getter/setter cache the "color" => engine representation conversion where most (all?) engines convert to an enum as there's a specific method for every property.

Note we'd still need .get(name) and .set(name) to deal with custom properties, since we don't want to add more named getters, ex. map.get("--foo"). vs map["--foo"].

The disadvantage of this approach is that it means StyleMap has 400+ properties like CSSStyleDeclaration does, and every new CSS property is implicitly adding new properties. It also means if maps get a new method called "filter", and we wanted StyleMap to be really maplike, we'd end up colliding with CSS's filter property.

@bzbarsky

[bzbarsky]

The name collision thing can be addressed by having an extra object:

element.styleMap.makeUpNameHere.color

That doesn't do anything for the other disadvantages, though.

[shans]

Another disadvantage is that people might think
element.styleMap.color.red += 20;
should work.

[css-meeting-bot]

The CSS Working Group just discussed #310, and agreed to the following resolutions:

RESOLVED: using properties (issue #310) is moved to L2

The full IRC log of that discussion

<shane> Topic: https://github.com/w3c/css-houdini-drafts/issues/310
<dbaron> Github topic: https://github.com/w3c/css-houdini-drafts/issues/310
<fantasai> shane: I want to either say No or wait until level 2 to consider this
<fantasai> Rossen: I'd be fine for that
<fantasai> RESOLVED: using properties (issue #310) is moved to L2